feat(sdk): add Swift and Kotlin mobile client foundations with push token proto

Swift SDK: Swift Package wrapping libquicproquo_ffi with QpqClient class
(connect, login, send, receive, disconnect) for iOS 15+ / macOS 13+.

Kotlin SDK: JNI bridge to libquicproquo_ffi with QpqClient class for
Android (aarch64, armv7) and JVM, Gradle build configuration.

Adds RegisterPushToken RPC (method ID 710) to device.proto for
APNs/FCM/WebPush device push token registration.

sdks/kotlin/build.gradle.kts

@@ -0,0 +1,23 @@
+plugins {
+    kotlin("jvm") version "1.9.22"
+}
+
+group = "dev.quicproquo"
+version = "0.1.0"
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation("com.google.code.gson:gson:2.10.1")
+    testImplementation(kotlin("test"))
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+kotlin {
+    jvmToolchain(17)
+}